At the present time, generally and widely used magnetic media contain thermoplastic resins such as vinyl chloride-vinyl acetate resins, vinyl chloride-vinylidene chloride resins, cellulose resins, acetal resins, urethane resins, acrylonitrile-butadiene resins and the like, alone or in combination as binder. However, the use of such binders results in inferior abrasion resistance which causes stains on the running path of the magnetic tape.
Furthermore, the methods employing thermosetting resins such as melamine resin, urea resin, etc., and the methods adding a chemically cross-linkable binding agent such as isocyanate compound, epoxy compound, etc., to the above mentioned thermoplastic resin are known. However, the use of cross-linkable binding agent has serious drawbacks such as: (1) the resin solution dispersed with magnetic substance shows poor storage stability, i.e., short pot life, which causes lack of uniformity of physical properties of magnetic coating composition and therefore homogeneity of magnetic tape, and (2) after coating and drying, heat treatment process is necessary for hardening the coating layer, which requires a long period for the production of commercial products.
For the purpose of preventing these drawbacks, methods for the production of magnetic materials employing oligomers and monomers of acrylic acid esters as binding agents and hardening them by irradiation of electron beam are disclosed in Japanese Patent Publication No. 12423/72, Japanese Patent Application (OPI) Nos. 15104/72, 77433/75, 86130/82 and 127926/82 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), U.S. Pat. No. 3,871,908 and British Pat. Nos. 2,055,877-B and 2,084,589. However, the methods disclosed in the above preceding technique did not afford magnetic recording media with excellent electromagnetic properties and high durability.
Recently, the improvement of tape skew has been highly desired in the field of small video tape for household use. Furthermore, video tape has been used under rigorous conditions due to the multifunctionalization of video tape recorder. However, there exists no tape having improved electromagnetic properties, tape skew and durability which satisfies the above mentioned requirements.